Pixel structure

ABSTRACT

A fabrication method of a pixel structure includes the following steps. A first metal layer is patterned to form a source electrode and a drain electrode. A semiconductor material layer is patterned to form a channel layer and a pixel pattern. A first insulation layer is formed to cover the channel layer, the source electrode, the drain electrode and the pixel pattern. A gate electrode is formed on the first insulation layer located above the channel layer. A second insulation layer is formed to cover the gate electrode and the first insulation layer. A pixel opening is formed in the first insulation layer and the second insulation layer to expose a partial region of the pixel pattern. The partial region of the pixel pattern exposed by the pixel opening is modified so as to form a pixel electrode electrically connected to the drain electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of and claims priority benefit of U.S.patent application Ser. No. 14/221,262 filed on Mar. 20, 2014, nowpending, which claims the priority benefit of Taiwan application serialno. 102140317, filed on Nov. 6, 2013. The entirety of each of theabove-mentioned patent applications is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a pixel structure and a fabrication methodthereof, and more particularly, relates to a pixel structure having amodified pixel electrode and a fabrication method thereof.

2. Description of Related Art

An electroluminescent device is a self-emissive device. Theelectroluminescent device has many advantages, such as no viewing anglerestriction, low fabrication cost, high response speed, low powerconsumption, a direct current driving function applicable to a portabledevice, a wide operating temperature range, light weight, and theability to be miniaturized and thinner together with the hardware, andso on. As the electroluminescent device has such great potential indevelopment, it is expected to become the next generation innovativeflat display panel.

Generally speaking, the electroluminescent device is composed of anupper electrode layer, a lower electrode layer, and a light-emittinglayer sandwiched between the two electrode layers. The lower electrodelayer is usually made of a transparent conductive material, so the lightgenerated by the light-emitting layer can penetrate through. The lowerelectrode layer is generally formed by a pixel electrode of a pixelstructure. However, several photo-mask processes are normally requiredin order to fabricate the pixel structure, in which several insulationlayers are located between the pixel electrode and a substrate.Therefore, as the light penetrates in a direction from the substratetoward the pixel electrode, it is likely causing the electroluminescentdevice to receive phenomena, such as insufficient illumination intensityfor displaying and color shift, etc.

SUMMARY OF THE INVENTION

The invention provides a pixel structure and a fabrication methodthereof, in which the fabrication method is simple and the pixelstructure has ideal illumination intensity for displaying.

A fabrication method of a pixel structure of the invention includesfollowing steps. A semiconductor material layer and a first metal layerare sequentially formed on a substrate. The first metal layer ispatterned to form a source electrode and a drain electrode. Thesemiconductor material layer is patterned to form a channel layer and apixel pattern, which the source electrode and the drain electrode aredisposed on the channel layer. A first insulation layer is formed on thesubstrate, which the first insulation layer covers the channel layer,the source electrode, the drain electrode, and the pixel pattern. A gateelectrode is formed on the first insulation layer located above thechannel layer. A second insulation layer is formed on the substrate, andthe second insulation layer covers the gate electrode and the firstinsulation layer. A pixel opening is formed in the first insulationlayer and the second insulation layer to expose at least one partialregion of the pixel pattern. The at least one partial region of thepixel pattern exposed by the pixel opening is modified to form a pixelelectrode electrically connected to the drain electrode.

A fabrication method of a pixel structure of the invention includesfollowing steps. A semiconductor material layer is formed on asubstrate. The semiconductor is patterned to form a channel pattern anda pixel pattern, in which the channel pattern includes a first regionand two second regions located at both sides of the first region. Afirst insulation layer is formed on the channel pattern, and the firstinsulation layer covers the first region of the channel pattern. A gateelectrode is formed on the first insulation layer. A metal layer isformed to cover the second regions of the channel pattern and the gateelectrode. As the metal layer is modified to form a metal oxide layer,the second regions contacted with the metal layer form a sourceelectrode and a drain electrode which are separated from each other. Thepixel pattern contacted with the metal layer forms a pixel electrodeelectrically connected to the drain electrode. A second insulation layeris formed on the substrate, and the second insulation layer covers thesource electrode, the drain electrode, the gate electrode, and the pixelelectrode. A pixel opening is formed in the second insulation layer andthe metal oxide layer, which the pixel opening exposes at least onepartial region of the pixel electrode.

A pixel structure of the invention is disposed on a substrate. The pixelstructure includes a channel layer, a source electrode, a drainelectrode, a pixel electrode, a first insulation layer, a gateelectrode, and a second insulation layer. The channel layer is disposedon the substrate. The source electrode is disposed on the channel layer.The drain electrode is disposed on the channel layer, which the sourceelectrode and the drain electrode are separated from each other. Thepixel electrode is disposed on the substrate and is electricallyconnected to the drain electrode. The channel layer and the pixelelectrode include a semiconductor material layer, in which the oxygencontent of the pixel electrode is lower than the oxygen content of thechannel layer. The first insulation layer covers the channel layer. Thegate electrode is disposed on the first insulation layer located abovethe channel layer. The second insulation layer covers the gate electrodeand the first insulation layer, which the second insulation layer has apixel opening. The pixel opening exposes at least one partial region ofthe pixel electrode.

Based on the above, the channel layer and the pixel pattern aresimultaneously formed by the fabrication method of the pixel electrodeof the invention. Also, the pixel pattern is modified to form the pixelelectrode having electrical conductor characteristics; and thefabrication process is simple so as to reduce the fabrication cost.Further, when the pixel electrode is used as a transparent lowerelectrode of the electroluminescent device, there is almost noinsulation layer between the pixel electrode and the substrate, therebyensuring sufficiency of the illumination intensity for displaying andreducing the color shift.

In order to make the aforementioned and other features and advantages ofthe invention more comprehensible, several embodiments accompanied withfigures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 1E are schematic cross-sectional views of a fabricationprocess of a pixel structure of an embodiment of the invention.

FIG. 1F is a schematic cross-sectional view of an electroluminescentdevice of another embodiment of the invention.

FIG. 2 is a schematic top view of the pixel structure of the embodimentof FIG. 1E.

FIG. 3 is a schematic cross-sectional view of a pixel structure ofanother embodiment of the invention.

FIG. 4A to FIG. 4F is schematic cross-sectional views of a fabricationprocess of a pixel structure of another embodiment of the invention.

FIG. 5 is a schematic top view of the pixel structure of the embodimentof FIG. 4F.

FIG. 6 is a schematic cross-sectional view of a pixel structure ofanother embodiment of the invention.

FIG. 7 is a plot of current-voltage relationships of an active device ofan embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1A to FIG. 1E are schematic cross-sectional views of a fabricationprocess of a pixel structure of an embodiment of the invention. FIG. 2is a schematic top view of the pixel structure of the embodiment of FIG.1E, and the cutting-plane position of FIG. 1A to FIG. 1E is referring tothe position of the cutting line depicted in FIG. 2. In order to clearlyillustrate locations of components of the pixel structure, some of thecomponents are omitted in FIG. 2.

Referring to FIG. 1A and FIG. 2, first, a semiconductor material layer104 and a first metal layer 106 are formed on a substrate 102. Thematerial of the semiconductor material layer 104 includesIn_((2-x))M3_((x))O₃[Zn_((1-y))M2_((y))O]_(m)N_((z)), where 0≦x≦2,0≦y≦1, 0≦m<6, 0≦z≦1, and M2 and M3 each independently represents Mg, Ca,Sr, Hf, Zn, Sn, B, Al, Ga, Y, or La. The electron mobility of thesemiconductor material layer 104 increases with increasing carrierconcentration. The material of the first metal layer 106 includes Al, astack film of MoN/Al, a stack film of MoN/Al/MoN, a stack film ofTi/Cu/Ti, a stack film of Ti alloy/Cu/Ti alloy, a stack film ofMoN/AlNd, a stack film of Ti/AlNd, or a stack film of Ti alloy/AlNd.

Referring to FIG. 1B and FIG. 2, the semiconductor material layer 104and the first metal layer 106 are patterned to form a source electrodeS, a drain electrode D, a lower electrode 108, a data line DL, a lowerconductive layer 110, a channel layer CH, a pixel pattern 112, and aplurality of pad layers 114 a, 114 b and 114 c. The source electrode S,the drain electrode D, the lower electrode 108, the data line DL, andthe lower conductive layer 110 are in the same layer. The channel layerCH, the pixel pattern 112, and the pad layers 114 a, 114 b and 114 c arein the same layer. In detail, the semiconductor material layer 104 ispatterned by undergoing a half tone mask process to form the channellayer CH, the pixel pattern 112, and the pad layers 114 a, 114 b and 114c. At this point, a portion of the first metal layer 106 to be patternedstill remains on the channel layer CH, the pixel pattern 112, and thepad layers 114 a, 114 b and 114 c. Then, the portion of the first metallayer 106 to be patterned again undergoes the half tone mask process toform the source electrode S, the drain electrode D, the lower electrode108, the data line DL, and lower conductive layer 110. Namely, in theembodiment, a same photo-mask process is used to form the sourceelectrode S, the drain electrode D, the channel layer CH, and the pixelpattern 112.

In the embodiment, the source electrode S and the drain electrode D aredisposed on the channel layer CH, and the source electrode S and thedrain electrode D are separated from each other. The lower electrode 108is disposed on the pad layer 114 a. The data line DL is disposed on thepad layer 114 b. The lower conductive layer 110 is disposed on the padlayer 114 c. Namely, the pad layer 114 a is located between thesubstrate 102 and the lower electrode 108. The pad layer 114 b islocated between the substrate 102 and the data line DL. The pad layer114 c is located between the substrate 102 and the lower conductivelayer 110.

Next, referring to FIG. 1C and FIG. 2, a first insulation layer 116 isformed on the substrate 102. The first insulation layer 116 covers thesource electrode S, the drain electrode D, the channel layer CH, thepixel pattern 112, the lower electrode 108, and the data line DL. Thefirst insulation layer 116 has a plurality of contact windows to exposesome components, which the contact windows, for example, are formed by aphoto-mask process. Specifically, a first contact window C1 exposes apartial region of the source electrode S. A second contact window C2exposes a partial region of a power line PL. A third contact window C3exposes a partial region of the drain electrode D. A fourth contactwindow C4 exposes a partial region of the pixel pattern 112. A fifthcontact window C5 exposes the lower conductive layer 110. The materialof the first insulation layer 116 includes titanium oxide (TiO_(x)),silicon oxide (SiO_(x)), silicon nitride (SiN_(x)), silicon oxynitride(SiON), aluminum oxide (AlO_(x)), zirconium oxide (ZrO_(x)), hafniumoxide (HfO_(x)), magnesium zirconium oxide (MgZrO_(x)), barium titaniumoxide (BaTiO_(x)), (x is greater than 1), or a stack layer thereof.

Next, referring to FIG. 1D and FIG. 2, a patterned metal layer is formedon the substrate 102, which a source electrode connection line SC, agate electrode G, a drain electrode connection line DC, a upperelectrode 118, a scan line SL, and a upper conductive layer 120 areformed on the first insulation layer 116 by a photo-mask process, forexample. Namely, the source electrode connection line SC, the gateelectrode G, the drain electrode connection line DC, the upper electrode118, the scan line SL, and the upper conductive layer 120 are in thesame layer. Specifically, the gate electrode G is disposed on the firstinsulation layer 116 located above the channel layer CH. The sourceelectrode connection line SC is electrically connected to the sourceelectrode S and the power line PL via the first contact window C1 andthe second contact window C2, respectively, as shown in the schematictop view of FIG. 2. An electrical current source is provided by thepower line PL to the source electrode S via the source electrodeconnection line SC. The drain electrode connection line DC is connectedto the drain electrode D via the third contact window C3, and the drainelectrode connection line DC is further connected to the pixel pattern112 via the fourth contact window C4. The upper electrode 118 isdisposed on the first insulation layer 116 located above the lowerelectrode 108, which the corresponding upper electrode 118 and the lowerelectrode 108 may form a storage capacitor CS. The upper conductivelayer 120 is disposed on the lower conductive layer 110, where the upperconductive layer 120 and the lower conductive layer 110 directly contacteach other to form a pad PD. The pad PD is, for example, located at anend of the data line DL or scan line SL as a conductive structure forbeing electrically connected to a printed circuit board or a drivingchip.

Next, referring to FIG. 1E and FIG. 2, a second insulation layer 122 isformed on the substrate 102, and a pixel opening 124 is formed in thefirst insulation layer 116 and the second insulation layer 122 by aphoto-mask process to expose a partial region of the pixel pattern 112.However, the invention should not be limited to those described herein.In the other embodiment, an opening is formed in the second insulationlayer 122, and subsequently, another opening is formed in the firstinsulation layer 116, which the two openings together form a pixelopening 124 to expose a partial region of the pixel pattern 112. Thensecond insulation layer 122 covers the upper electrode 118 and the scanline SL, and the second insulation layer 122 exposes the upperconductive layer 120. Next, the partial region of the pixel pattern 112exposed by the pixel opening 124 is modified to form a pixel electrodePE. Specifically, the second insulation layer 122 includes a firstmaterial layer 122 a and a second material layer 122 b. The material ofthe first material layer 122 a includes titanium oxide (TiO_(x)),silicon oxide (SiO_(x)), silicon nitride (SiN_(x)), silicon oxynitride(SiON), aluminum oxide (AlO_(x)), zirconium oxide (ZrO_(x)), hafniumoxide (HfO_(x)), magnesium zirconium oxide (MgZrO_(x)), barium titaniumoxide (BaTiO_(x)), (x is greater than 1), or a stack layer thereof. Thematerial of the first material layer 122 a may include an organicmaterial, for example, hydrocarbons (C_(x)O_(y)H_(z), where x, y and zare greater than 1). The material of the second material layer 122 bincludes titanium oxide (TiO_(x)), silicon oxide (SiO_(x)), siliconnitride (SiN_(x)), silicon oxynitride (SiON), aluminum oxide (AlO_(x)),zirconium oxide (ZrO_(x)), hafnium oxide (HfO_(x)), magnesium zirconiumoxide (MgZrO_(x)), barium titanium oxide (BaTiO_(x)), (x is greater than1), or a stack layer thereof. The material of the second material layer122 b may also include an organic material, for example, hydrocarbons(C_(x)O_(y)H_(z), where x, y and z are greater than 1). Here, the secondinsulation layer 122 including two material layers is for illustrationpurpose; however, the invention does not pose any limitation to thenumber of material layers in the second insulation layer 122.

Specifically, the afore method of modifying the pixel pattern 112 is,for example, performing a nitrogen annealing process on the partialregion of the pixel pattern 112 exposed by the pixel opening 124. Thetemperature of the nitrogen annealing process is about 150° C. to 450°C. The partial region of the pixel pattern 112 exposed by the pixelopening 124 is converted into a conductor portion 126 having conductorcharacteristics after performing the nitrogen annealing process. Theoxygen content of the conductor portion 126 is less than 4 at % (atomicpercent). A partial region of the pixel pattern 112 covered by the firstinsulation layer 116 and the second insulation layer 122 is unaffectedby the nitrogen annealing process, which maintains the characteristicsof semiconductor and then form a semiconductor portion 128. The oxygencontent of the semiconductor portion 128 is equal to or greater than 4at % (atomic percent). The conductor portion 126 and the semiconductorportion 128 constitute the pixel electrode PE. The pixel electrode PEand the channel layer CH are located on the same surface. In theembodiment, four photo-mask processes are used to complete thefabrication of the pixel structure 100, such that the fabricatingprocess is relatively simplified, thereby reducing the fabrication cost.

In another aspect, the pixel electrode PE and the channel layer CH bothinclude the semiconductor material layer, which the oxygen content ofthe conductor portion 126 of the pixel electrode PE is lower than theoxygen content of the channel layer CH. The oxygen content of theconductor portion 126 of the pixel electrode PE is less than 4 at %. Theoxygen content of the channel layer CH is equal to or greater than 4 at%. The oxygen content of the semiconductor material layer affects thesheet resistance thereof. In the embodiment, the sheet resistance of theconductor portion 126 of the pixel electrode PE is roughly less than120Ω/□. The sheet resistance of the channel layer CH is roughly greaterthan 1500Ω/□. Further, the pixel electrode PE includes the conductorportion 126 and the semiconductor portion 128. The conductor portion 126has transparent electrical conductive properties; therefore theconductor portion 126 may be used as a transparent lower electrode of anelectro-luminescence device. Specifically, as shown in FIG. 1F, alight-emitting layer 130 and an upper electrode layer 132 may bedisposed in the pixel opening 124 so as to form a pixel structure 100 aof the electro-luminescence device. In the embodiment, the pixelelectrode PE is directly disposed on the substrate 102. In aconventional electro-luminescence device, several insulation layers areinterposed between the lower electrode and the substrate. Hence,compared with the conventional electro-luminescence device, since thepixel electrode PE of the embodiment takes a role of the transparentlower electrode of the electro-luminescence device, strongerillumination intensity for display is maintained and a color shiftphenomenon is rare to occur when the light emits from the pixelelectrode PE toward the substrate 102.

In the embodiment, the source electrode S, the drain electrode D, thechannel layer CH, and the gate electrode G generally constitute a firstactive device T1. Besides, the pixel structure 100 may further include asecond active device T2 so as to form a circuit structure having twoactive devices and one capacitor (i.e., 2T1C). Namely, the pixelstructure 100 a of the electro-luminescence device of the embodiment isdriven by the circuit structure having 2T1C, in which the active devicesT1 and T2 are, for example, top gate electrode thin film transistors.However, the circuit structure having 2T1C is exemplified herein forillustration purposes; the invention does not pose any limitationthereto.

The evaluation of the first active device T1 of the pixel structure 100of the embodiment is shown in FIG. 7. According to FIG. 7, the firstactive device T1 has a good electrical performance, where the carriermobility of the first active device T1 is greater than 20 cm²/Vs.

In the embodiment, the semiconductor portion 128 of the pixel electrodePE and the channel layer CH are separated from each other and connectedto the drain electrode connection line DC. Therefore, the pixelelectrode PE electrically connects to the drain electrode D via thedrain electrode connection line DC, which however should not beconstrued as a limitation to the invention. In the embodiment of FIG. 3,the semiconductor portion 128 of the pixel electrode PE and the channellayer CH are connected with each other, thereby the pixel electrode PEis directly electrically connected to the drain electrode D via thechannel layer CH.

FIG. 4A to FIG. 4F is schematic cross-sectional views of a fabricationprocess of a pixel structure of another embodiment of the invention.FIG. 5 is a schematic top view of the pixel structure of the embodimentof FIG. 4F, which the cutting-plane position of FIG. 4A to FIG. 4F isreferring to the position of the cutting line depicted in FIG. 5. Inorder to clearly illustrate locations of components of the pixelstructure, some of the components such as insulation layers are omittedin FIG. 5.

Referring to FIG. 4A and FIG. 5, first, a semiconductor material layer204 is formed on a substrate 202. The material of the semiconductormaterial layer 204 includesIn_((2-x))M3_((x))O₃[Zn_((1-y))M2_((y))O]_(m)N_((z)), where 0≦x≦2,0≦y≦1, 0≦m<6, 0≦z≦1, and M2 and M3 each independently represents Mg, Ca,Sr, Hf, Zn, Sn, B, Al, Ga, Y, or La.

Referring to FIG. 4B and FIG. 5, the semiconductor material layer 204 ispatterned to form a channel pattern 206, a pixel pattern 208, acapacitor pattern 210, and a pad pattern 212 by a photo-mask process.The channel pattern 206 includes a first region 206 a and two secondregions 206 b, in which the second regions 206 b are located at bothsides of the first region 206 a. The capacitor pattern 210 includes athird region 210 a and two fourth regions 210 b, in which the fourthregions 210 b are located at both sides of the third region 210 a.

Next, referring to FIG. 4C and FIG. 5, an insulation material layer (notillustrated) and a metal material layer (not illustrated) are formed onthe substrate 202. The insulation material layer and the metal materiallayer are patterned to form a first insulation layer 214 and a patternedmetal layer by a photo-mask process. The material of the insulationmaterial layer includes titanium oxide (TiO_(x)), silicon oxide(SiO_(x)), silicon nitride (SiN_(x)), silicon oxynitride (SiON),aluminum oxide (AlO_(x)), zirconium oxide (ZrO_(x)), hafnium oxide(HfO_(x)), magnesium zirconium oxide (MgZrO_(x)), barium titanium oxide(BaTiO_(x)), (x is greater than 1), or a stack layer thereof. Thematerial of the insulation material layer may include an organicmaterial, for example, hydrocarbons (C_(x)O_(y)H_(z), where x, y and zare greater than 1). The material of the metal material layer includesAl, a stack film of MoN/Al, a stack film of MoN/Al/MoN, a stack film ofTi/Cu/Ti, a stack film of Ti alloy/Cu/Ti alloy, a stack film ofMoN/AlNd, a stack film of Ti/AlNd, or a stack film of Ti alloy/AlNd. Thepatterned metal layer is located on the first insulation layer 214 andincludes a gate electrode G, an upper electrode 216 and a scan line SL.Specifically, the first insulation layer 214 covers the first region 206a of the channel pattern 206 and the third region 210 a of the capacitorpattern 210. The gate electrode G is located on the first insulationlayer 214 located above the first region 206 a. The upper electrode 216is located on the first insulation layer 214 located above the thirdregion 210 a.

Next, a metal layer 218 is formed on the substrate 202. The metal layer218 at least covers the second regions 206 b of the channel pattern 206,the gate electrode G, the pixel pattern 208, the fourth regions 210 b ofthe capacitor pattern 210, the upper electrode 216, the scan line SL,and the pad pattern 212. The material of the metal layer 218 includesAl, Ti, Si, or Mo. The thickness of the metal layer 218 is, for example,less than 150 Å.

Referring to FIG. 4C, FIG. 4D and FIG. 5, the metal layer 218 ismodified to form a metal oxide layer 220. In particular, the method ofmodifying the metal layer 218 is, for example, performing an oxygenannealing process so as to make the metal layer 218 be oxidized to forma metal oxide layer 220. The temperature of the oxygen annealing processis about 150° C. to 450° C. Here, the metal oxide layer 220 is treatedas an insulation material. The regions contacted with the metal layer218 of the channel pattern 206, the pixel pattern 208, the capacitorpattern 210 and the pad pattern 212 are affected by the temperature ofthe oxygen annealing process and thus the material properties thereofare changed. For instance, a semiconductor is modified into a conductor.After performing the oxygen annealing process, a source electrode S, adrain electrode D, a conductor portion 222, a semiconductor portion 224,a lower electrode 226, a lower conductive layer 228, and a pad layer 229may be formed.

Specifically, the second regions 206 b of the channel pattern 206connected with the metal layer 218 form the source electrode S and thedrain electrode D which are separated from each other. The first region206 a of the channel pattern 206 forms a channel layer CH, where thechannel layer CH is located between the source electrode S and the drainelectrode D. In the embodiment, the un-modified channel pattern 206under the source electrode S and the drain electrode D is treated as aportion of the channel layer CH.

A surface portion of the pixel pattern 208 contacted with the metallayer 218 forms the conductor portion 222. The other portion of thepixel pattern 208 not contacted with the metal layer 218 forms thesemiconductor portion 224. The oxygen content of the conductor portion222 is less than 4 at %, and the oxygen content of the semiconductorportion 224 is equal to or greater than 4 at %. The conductor portion222 and the semiconductor portion 224 constitute a pixel electrode PE.The semiconductor portion 224 is located between the conductor portion222 and the substrate 202. In the embodiment, the pixel electrode PE andthe channel layer CH are in the same layer. The pixel electrical PE andthe channel layer CH are located on the same surface.

In another aspect, the pixel electrode PE and the channel layer CH bothinclude the semiconductor material layer, which the oxygen content ofthe conductor portion 222 of the pixel electrode PE is lower than theoxygen content of the channel layer CH. The oxygen content of theconductor portion 222 of the pixel electrode PE is less than 4 at %. Theoxygen content of the channel layer CH is equal to or greater than 4 at%. The oxygen content of the semiconductor material layer affects thesheet resistance thereof. In the embodiment, the sheet resistance of theconductor portion 222 of the pixel electrode PE is roughly less than120Ω/□, and the sheet resistance of the channel layer CH is roughlygreater than 1500Ω/□.

The fourth regions 210 b of the capacitor pattern 210 contacted with themetal layer 218 form two modified portions 226 b. The third region 210 aof the capacitor pattern 210 forms an un-modified portion 226 a. Themodified portions 226 b are located at both sides of the urn-modifiedportion 226 a. The modified portions 226 b, the source electrode S, andthe drain electrode D are in the same layer. The first insulation layer214 covers the un-modified portion 226 a. The un-modified portion 226 aand the modified portions 226 b together constitute the lower electrode226.

A surface portion of the pad pattern 212 contacted with the metal layer218 forms the lower conductive layer 228. The lower conductive layer228, the source electrode S, and the drain electrode D are in the samelayer. The un-modified pad pattern 212 located under the lowerconductive layer 228 forms the pad layer 229, which the pad layer 229 islocated between the lower conductive layer 228 and the substrate 202.

Next, referring to FIG. 4E and FIG. 5, a second insulation layer 230 isformed on the substrate 202. A pixel opening 232 is formed in the secondinsulation layer 230 by a photo-mask process to expose a partial regionof the conductor portion 222 of the pixel electrode PE. The secondinsulation layer 230 covers the metal oxide layer 220. In particular,the second insulation layer 230 includes a first material layer 230 aand a second material layer 230 b, in which the first material layer 230a covers the metal oxide layer 220. The material of the first materiallayer 230 a includes titanium oxide (TiO_(x)), silicon oxide (SiO_(x)),silicon nitride (SiN_(x)), silicon oxynitride (SiON), aluminum oxide(AlO_(x)), zirconium oxide (ZrO_(x)), hafnium oxide (HfO_(x)), magnesiumzirconium oxide (MgZrO_(x)), barium titanium oxide (BaTiO_(x)), (x isgreater than 1), or a stack layer thereof. The material of the firstmaterial layer 230 a may include an organic material, for example,hydrocarbons (C_(x)O_(y)H_(z), where x, y and z are greater than 1). Thematerial of the second material layer 230 b includes titanium oxide(TiO_(x)), silicon oxide (SiO_(x)), silicon nitride (SiN_(x)), siliconoxynitride (SiON), aluminum oxide (AlO_(x)), zirconium oxide (ZrO_(x)),hafnium oxide (HfO_(x)), magnesium zirconium oxide (MgZrO_(x)), bariumtitanium oxide (BaTiO_(x)), (x is greater than 1), or a stack layerthereof. The material of the second material layer 230 b may alsoinclude an organic material, for example, hydrocarbons (C_(x)O_(y)H_(z),where x, y and z are greater than 1). Here, the second insulation layer230 including two material layers is for illustration purpose; however,the invention does not pose any limitation to the number of materiallayers in the second insulation layer 230.

The second insulation layer 230 and the metal oxide layer 220 furtherhave a plurality of contact windows to expose some components. Thecontact windows are, for example, formed simultaneously with the pixelopening 232. Namely, when forming the contact windows, in addition toremove a portion of the second insulation layer 230, a portion of themetal oxide layer 220 is further removed to expose some components. Indetail, a sixth contact window C6 exposes a partial region of the sourceelectrode S. A seventh contact window C7 exposes a partial region of thedrain electrode D. An eighth contact window C8 exposes a partial regionof the pixel electrode PE. A ninth contact window C9 and a tenth contactwindow C10 expose the modified portion 226 b of the lower electrode 226.An eleventh contact window C11 exposes the lower conductive layer 228.

Then, referring to FIG. 4F and FIG. 5, a patterned metal layer is formedon the substrate 202, which a power line PL, a source electrodeconnection line SC, a drain electrode connection line DC, a capacitorconnection line CC, a data line DL, and an upper conductive layer 234are formed on the second insulation layer 230 by a photo-mask process,for example. Namely, the power line PL, the source electrode connectionline SC, the drain electrode connection line DC, the capacitorconnection line CC, the data line DL and the upper conductive layer 234are in the same layer. Particularly, the source electrode connectionline SC is connected to the power line PL, and the source electrodeconnection line SC is connected to the source electrode S via the sixthcontact window C6. Therefore, an electrical current source is providedby the power line PL to the source electrode S via the source electrodeconnection line SC. Here, as an exemplary, the power line PL and thesource electrode connection line SC are formed in a same photo-maskprocess; however the invention should not be limited to those describedherein. The power line PL and the source electrode connection line SCmay be fabricated by other process and in different layers.

The drain electrode connection line DC is connected to the drainelectrode D via the seventh contact window C7, and the drain electrodeconnection line DC is further connected to the pixel electrode PE viathe eighth contact window C8. The capacitor connection line CC isconnected to the lower electrode 226 via the ninth contact window C9 andthe tenth contact window C10. The upper conductive layer 234 isconnected to the lower conductive layer 228 via the eleventh contactwindow C11. The upper electrode 216 is disposed on the first insulationlayer 214 located above the lower electrode 226, in which thecorresponding upper electrode 216 and the lower electrode 226 are formeda storage capacitor CS. The upper conductive layer 234 is disposed onthe lower conductive layer 228, where the upper conductive layer 234 andthe lower conductive layer 228 directly contact with each other to forma pad PD. The pad PD is, for example, located at an end of the data lineDL or scan line SL as a conductive structure to electrically connect toa printed circuit board or a driving chip.

In the embodiment, the pixel electrode PE exposed by the pixel opening232 is directly disposed on the substrate 202. In a conventionalelectro-luminescence device, several insulation layers are interposedbetween the lower electrode and the substrate. Hence, compared with theconventional electro-luminescence device, since the pixel electrode PEof the embodiment takes a role of the transparent lower electrode of theelectro-luminescence device, stronger illumination intensity for displayis maintained and a color shift phenomenon is rare to occur when thelight emits from the pixel electrode PE toward the substrate 202. In theembodiment, four photo-mask processes are used to complete thefabrication of the pixel structure 200, such that the fabricatingprocess is relatively simplified, thereby reducing the fabrication cost.

In the embodiment, the source electrode S, the drain electrode D, thechannel layer CH, and the gate electrode G generally constitute a thirdactive device T3. Besides, the pixel structure 200 may further include afourth active device T4 so as to form a circuit structure having twoactive devices and one capacitor (i.e., 2T1C). Namely, thelight-emitting layer is driven by the circuit structure having 2T1C, inwhich the active devices T3 and T4 are, for example, top gate electrodethin film transistors. However, the circuit structure having 2T1C isexemplified herein for illustration purposes; the invention does notpose any limitation thereto.

In the embodiment, the pixel electrode PE and the channel layer CH areseparated from each other and connected to the drain electrodeconnection line DC. Therefore, the pixel electrode PE electricallyconnects to the drain electrode D via the drain electrode connectionline DC, which however should not be construed as a limitation to theinvention. In the embodiment of FIG. 6, the pixel electrode PE and thechannel layer CH are connected to each other, thereby the pixelelectrode PE is directly electrically connected to the drain electrodeD.

The afore-disclosures of FIG. 2 and FIG. 5 are applied to the design ofpixels of the electro-luminescence device. However, the method ofmodifying the pixel pattern to form the pixel electrode in the inventionis not limited to only be applied to the pixel structure of theelectro-luminescence device. In other words, the method of modifying thepixel pattern to form the pixel electrode in the invention can also beused in other processes requiring less photo-mask process to completethe pixel structure.

In summary, the pixel pattern and the channel layer are formedsimultaneously in the invention, and the pixel pattern is modified andforms the pixel electrode having the electrical conductor properties.This way, the number of the photo-mask process can be reduced, therebyreducing the fabrication cost. Further, when the pixel electrode is usedas a transparent lower electrode of the electroluminescent device, thereis almost no insulation layer interposed between the pixel electrode andthe substrate, thereby ensuring sufficiency of the illuminationintensity for displaying and reducing the color shift.

What is claimed is:
 1. A pixel structure, disposed on a substrate,comprising: a channel layer, disposed on the substrate; a sourceelectrode and a drain electrode, disposed on the channel layer, whereinthe source electrode and the drain electrode are separated from eachother; a pixel electrode, disposed on the substrate and electricallyconnected to the drain electrode, wherein the channel layer and thepixel electrode comprise a semiconductor material layer, and an oxygencontent of the pixel electrode is less than an oxygen content of thechannel layer; a first insulation layer, covering the channel layer; agate electrode, disposed on the first insulation layer located above thechannel layer; and a second insulation layer, covering the gateelectrode and the first insulation layer, wherein the second insulationlayer has a pixel opening, and the pixel opening exposes at least onepartial region of the pixel electrode.
 2. The pixel structure as claimedin claim 1, wherein the channel layer and the pixel electrode arelocated on a same surface.
 3. The pixel structure as claimed in claim 1,wherein the channel layer and the pixel electrode are made of the samesemiconductor material layer, and a material of the semiconductormaterial layer comprisesIn_((2-x))M3_((x))O₃[Zn_((1-y))M2_((y))O]_(m)N_((z)), where 0≦x≦2,0≦y≦1, 0≦m<6, 0≦z≦1, and M2 and M3 each independently represents Mg, Ca,Sr, Hf, Zn, Sn, B, Al, Ga, Y, or La.
 4. The pixel structure as claimedin claim 1, wherein the first insulation layer further covers the sourceelectrode and the drain electrode and exposes the at least one partialregion of the pixel electrode.
 5. The pixel structure as claimed inclaim 4, wherein the pixel electrode comprises a conductor portion and asemiconductor portion, the pixel opening exposes the conductor portionof the pixel electrode, and the first insulation layer and the secondinsulation layer cover the semiconductor portion of the pixel electrode.6. The pixel structure as claimed in claim 4, further comprising: afirst contact window and a second contact window, disposed in the firstinsulation layer, wherein the first contact window and the secondcontact window exposes the source electrode and the drain electrode,respectively; and a source electrode connection line and a drainelectrode connection line, disposed on the first insulation layer,wherein the source electrode connection line is connected to the sourceelectrode via the first contact window, and the drain electrodeconnection lien is connected to the drain electrode via the secondcontact window.
 7. The pixel structure as claimed in claim 4, furthercomprising a storage capacitor, wherein the storage capacitor comprisesa lower electrode, disposed on the substrate and further covering thelower electrode, wherein the lower electrode comprising a layeridentical to the source electrode and the drain electrode; and an upperelectrode, disposed on the first insulation layer located above thelower electrode, wherein the upper electrode and the gate electrode aremade of the same layer.
 8. The pixel structure as claimed in claim 1,further comprising a metal oxide layer, wherein the metal oxide layercovers the gate electrode, the first insulation layer, the sourceelectrode and the drain electrode and exposes the at least one partialregion of the pixel electrode, and the second insulation layer isdisposed on the metal oxide layer.
 9. The pixel structure as claimed inclaim 8, wherein the pixel electrode further comprises a conductorportion and a semiconductor portion, wherein the semiconductor portionis disposed on the substrate, the conductor portion is disposed on thesemiconductor portion, and the pixel opening exposes the conductorportion of the pixel electrode.
 10. The pixel structure as claimed inclaim 8, further comprising: a first contact window, a second contactwindow and a third contact window, disposed in the second insulationlayer and the metal oxide layer, wherein the first contact window andthe second contact window respectively expose the source electrode andthe drain electrode, and the third contact window exposes the pixelelectrode; and a source electrode connection line and a drain electrodeconnection inline, disposed on the second insulation layer, wherein thesource electrode connection line is connected to the source electrodevia the first contact window, the drain electrode connection line isconnected to the drain electrode and the pixel electrode via the secondcontact window and the third contact window.
 11. The pixel structure asclaimed in claim 8, further comprising a storage capacitor, wherein thestorage capacitor comprises a lower electrode, disposed on thesubstrate, wherein the lower electrode comprises a un-modified portionand two modified portions located at both sides of the un-modifiedportion, the modified portions, the source electrode and the drainelectrode are made of the same layer, and the first insulation layerfurther covers the un-modified portion; and an upper electrode, disposedon the first insulation layer located above the un-modified portion,wherein the upper electrode and the gate electrode are made of the samelayer.